Carbon fibre filled conductive composites based on nitrile rubber (NBR), ethylene propylene diene rubber (EPDM) and their blend

The conductivity of nitrile rubber (NBR), ethylene-propylene -diene rubber (EPDM) and 50/50 NBR/EPDM blend has been measured against the loading of conductive carbon fibre to check the percolation limit for each system. The volume resistivity of all fibre-rubber composites increases with the increase in temperature, and the rate of increase in resistivity against temperature depends on the loading of carbon fibre and the nature of the base polymer. The change in volume resistivity during the heating and cooling cycle does not follow the same route, leading to the phenomena of electrical hysteresis and electrical set. The current-voltage relation is linear at room temperature, but becomes nonlinear at higher temperature. Some mechanical properties of these composites are also measured. The applicability of different theoretical models to predict the modulus and conductivity of these systems has been tested. Deviations between theoretical and experimental values are also discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.